Radiator core construction



Aug. 4, 1953 Filed Aug. 17, 1951 E. LUDLOW RADIATOR CORE CONSTRUCTION 2 Sheets-Sheet l INVENTOR. zZ/m/nrp L up; on;

Aug. 4, 1953 E. LUDLOW RADIATOR CORE CONSTRUCTiON 2 Sheets-Sheet 2 Filed Aug. 17, 1951 INVENTOR. @MU/Vp L 09w v.5 BY

Patented Aug. 4, 1953 RADIATOR CORE CONSTRUCTION Edmund Ludlow,

Arvin Industries, ration of Indiana Columbus, Ind., assignor to 1110., Columbus, Ind., a corpo- Application August 17, 1951, Serial N o. 242,28l 3 Claims. (Cl. 257-130) This invention relates to heat exchangers of the general type exemplified by automobile radiators and the cores of hot-water heaters for use in automobiles. Such heat exchangers commonly employ a pair of spaced headers interconnected by a plurality of thin-walled, spaced tubes. Liquid flows through the tubes and air through the spaces between the tubes. To improve the rate of heat exchange between the liquid and the air, it is common to dispose in the spaces between the tubes metal heat-transfer elements which are in intimate heat-transferring relationship with the tubes and which present large areas for contact with the air flowing through the spaces between the tubes.

It is an object of this invention to improve the construction of the heat-transfer elements above referred to. A further object of the invention is to produce a heat-transfer element which will possess improved efiectiveness in transferring heat to the air flowing over it and which will not oppose undue resistance to the flow of such air. A further object of the invention is to provide a heat-transfer element which can be simply and economically constructed and readily assembled with the other elements of the heat-exchanger.

A heat-transfer element embodying my invention is perhaps most conveniently described as comprising an elongated strip of thin metal of relatively high heat-conductivity bent repeatedly and reversely along transverse lines to define transversely extending, spaced ribs. The side walls of such ribs are provided with parallel slits located in planes generally perpendicular to the ribs and dividing each rib into a plurality of ribportions. Adjacent rib-portions are offset from each other transversely of the rib, each slit thereby forming an opening which is presented longitudinally of the rib and which provides communication between the interior of the rib and the space between such rib and an adjacent rib. Preferably, the side walls of the individual ribportions are parallel to the direction of air flow through the core so that such side walls themselves do not tend to deflect the air laterally with respect to its general direction of flow. At each slit-formed opening, however, every air stream passing through a rib or through the space between ribs is divided; and as there are a multiplicity of slits in each rib, the division of each air stream is repeated many times as the air flows through the core. r

The accompanying drawing illustrates the invention: Fig. l is a section through a heatexchanger core on the line l..| of Fig. 2; Fig. 2

ribs are interconnected by inner walls 23.

, providing is a fragmental section on the line 22 of Fig. 1; Fig. 3.is a i'ragmental isometric view illustrating one of the heat-transfer elements; Fig. 4 illustrates a development into a plane of the heattransfer element shown in Fig. 3; Fig. 5 is a diagrammatic view illustrating the preferred arrangement of heat-exchanging elements in a core; Figs. 6 and 7 are fragmental views similar respectively to Figs. 3 and 4 but illustrating a modified construction; and Figs. 8 and 9 are also views respectively similar to Figs. 3 and 4 illustrating a further modification.

The heat-exchanger illustrated in Figs. 1 to 4 comprises an uppercheader ID, a lower header I I, and a plurality of wide, thin, flat-walled tubes l2 interconnecting such headers. In the particular arrangement illustrated, the upper header I0 is divided by a transverse partition B into two chambers l4 and I5 provided respectively with inlet and outlet openings l6 and I1. Liquid enters the opening [6 into the chamber [4, flows downwardly through thetubes l2 communicating with that chamber, transversely through the lower header II and upwardly through the remain: ing tubes into theoutlet chamber l5. The tubes I2 are shown as arranged in pairs, the two tubes of each pair being coplanar and spaced from the tubes of other pairs. In use, liquid circulates through the tubes l2 as previously described, air flows through the spaces between adjacent pairs of tubes, and an exchange of heat takes place between the air and the liquid.

My invention relates to heat-transfer elements which are disposed in the spaces between adjacent pairs of tubes I! in intimate heat-receiving relationship with the walls of the tubes and which project outwardly from the tubes to pre' sentlarge surface areas for contact with air flowing through the core. p preferred form of heattransfer element is illustrated in Figs. 1 to 4. Such heat-transfer element is formed of an elongated strip 20 of metal, such as copper, possessing high heat-conductivity. As will be clear from Figs. 2 and 3, the strip 20 is repeatedly and reversely bent to provide ribs extending transversely of the strip. Each such rib possesses an outer wall 2| and side walls 22, and adjacent The side walls of each rib are provided with slits 24 which, in effect, divide each rib into a multiplicity of rib-portions, and adjacent ones of those rib-portions are oifset from each other transversely of the rib so that the slits 24 form openings presented longitudinally of the rib. and communication betweenthe interior of stream is in turn subdivided repeatedly at the openings provided by the slits 24. I have found the division and repeated subdivisionoflfthe air stream to be very effective in improving vheat-v transference. g I I 7' In the preferred form of core, the offsetting between adjacent rib-portions is progressively in one direction from one: edge of the strip' 20 to the center thereof and is then-progressively in the opposite direction from the center to. the opposite edge of the strip. The aggregate amount of offsetlting'between each edge of the "strip and the center thereof desirably exceeds the width-of the'rib, so that it will be impossible for air to pass in a straight line through "the' core with'outencountering one of the slit-formed openings 24.

In the "developed viewconstituting Fig. i, it will be obvious that the slits 24 are arranged in transverse rows whichgenerally accord with the shape of the ribs in the finished heat-transfer element. "That is; the slits'24are arranged in transverse rows, the slits'in each row being offset fr.om*eachother progressively in one direction from one edge of the strip .to the center thereof, and then in theother'direction from the center to'the opposite edge ofthe strip. The slits are likewise arranged'in longitudinal rows, the slits in each longitudinal row being in alignment with each other. In Fig. 4, the dotted lines 25 represent the-lines at which folds exist in thefinished heat-transfer element.

' The-heat-transfer element described lends itf selfto' manufacture by inexpensive and simple equipment, as each element maybe formed in a single rolling operation which simultaneously bends'the metal and cuts the slits 24. Since the offsetting in each rib is in opposite directions from the center'of the strip 20 toward the edges thereof, any lateral:forc'esfexerted on the strip during the forming operation are balanced, and there is no tendency of the strip to move laterally of itself in the rollers which form it.

Conveniently, two of the heat-transfer eleinents are disposed between adjacent pairs of tubes I2, the'heat-transfereleinents extending for the full thickness of the core, and each element' having its'inner walls 23 in contact with the side walls of a pair of tubes l2 and its outer walls 2| incontact with the outer walls of the associated heat-transfer element. It will be obvious that-any heat-transfer element can be positioned in the core with the offsetting in each'rib progressing either downwardly orupwardly from the center of the element towardthe outer edges thereof. "For-convenience, I prefer. that the two heat-transfer elements located between adjacent pairs of tubes be"disposed-oppositely, as indicated in Fig. 5, so that the ribs of one of such elements cross the ribs of. the other.

1 Heat-transfer elements constructed in accordance with my invention possess several advantages in addition to'their effectiveness in dividing and subdividing the air which flows through the core. It will be noted,'for example, that the .inher, tube-engaging walls 23 of .ea'che'element' are essentially the same as 4 plane and uninterrupted. As a result, when, as a final step in core-assembly, the face of the core is immersed in molten solder, the solder will be drawn by capillary attraction between the tubewalls and the inner element-walls 23 to provide an efiective heat-transfer joint. It will also be noted that. theslits 24 lie in p-lanes-normal to the side-walls of the .tubes. 12 and hence do not cut across and interrupt the lines of heat flow in the heat-transfer element.

The modification illustrated in Figs. 6 and '7 is that shown in Figs. 1 to 4 except for the fact that the slits 24a are longer than thefslits' 24 and extend across the outer rib wall 2| as-well asacross the side walls.

The modification illustrated in Figs. 8 and 9 differs from that of Figs. 3 and 4 in that the slits 24b, in any one transverse row are not offset from each other longitudinally of the strip. The fold lines 25 in the modification of Figs. 8 and 9 do not extend perpendicularly-of the slits, but instead depart from perpendicularity by a slight amount, as indicated, to provide the desired offsetting of the rib-sections.

All modifications shown have in common the fact that the slits are arranged in longitudinal and transverse rows and that each fold line 25 marking the junction of a side wall 22 and the contiguous inner, wall 23 extends from one end of a slit in one longitudinal row to a point intermediate the ends of the corresponding slit in the next longitudinal row.

I claim asmy invention:

1. A heat-transfer element for usein a heatexchanger, comprising an elongated metal strip provided with transversely extending rows of parallel, longitudinally extending slits ofsubstantially equal length, adjacent slits of each TOW being offset from each other longitudinally of the strip for a distance equal to a small fraction of the slit-length, the metal between adjacent slits and between the 'end slit of each row a the adjacent strip-edge being offset from he plane of the strip toform similar channel-like rib positions, adjacent rib-portions being offset from each otherby a'distance substantially equal to the offsetting of adjacent slits, the offsetting of the slits and ribs continuing in one direction until at the center of the strip the ag re a amount of offsetting is at least equal to the width of the rib-portions, the offsetting then proceeding similarly but in the opposite direction for the balance of the strip-width.

2. A heat-transfer element for use in a heatexchanger, comprising an elongated metal strip provided with transversely extending rows of parallel, longitudinally extending slits of Substantially equal length, adjacent slits of each row being offset'f'rom each other longitudinally of the Strip for a distance equal to a small fraction of the slit-length, the metal between adjacent slits and between the end slit of each row and the adjacent strip-edge being ofiset from the plane of the strip to form similar channel-like rib portions, adjacent rib-portions being offset from each other'bya distance substantially equal to the offsetting of adjacent slits, the offsetting of the slits and ribs'continuing in one direction until the aggregate amount of oifsetting is at least equal to the width of the rib-portions.

3. A heat-transfer element for use in a heatexchanger, comprising an elongated metal strip provided .with' transversely extending rows Of parallel, longitudinally extending slits of substantially. equal length; adjacent slits of each row being offset from each other longitudinally of the strip for a distance equal to a small fraction of the slit-length, the metal between adjacent slits and between the end slit of each row and the adjacent strip-edge being offset from the plane of the strip to form similar channellike rib portions, adjacent rib-portions being offset from each other by a distance substantially equal to the offsetting of adjacent slits.

EDMUND LUDLOW.

References Cited in the file of this patent UNITED STATES PATENTS Number 5 1,802,263 1,939,175 2,133,502

Number 438,948

Name Date Medville Apr. 21, 1931 Kramer Dec. 12, 1933 Emmons Oct. 18, 1938 FOREIGN PATENTS Country Date France -a Jan. 13, 1912 

